1. Field of the Invention
The present invention relates to a communication path switching apparatus, a communication path switching method, and computer program product for controlling communication path switching system. In particular, the present invention relates to a communication path switching apparatus and a communication path switching method which can preferably be used for a sub rate switch of a line exchanger containing an ISDN basic interface (2B+D) or a line exchanger for multiplexing a compressed voice signal with a low-speed data as well as to a recording medium.
2. Description of the Related Art
For example, Japanese Patent Publication (Unexamined) A4-180499 discloses a xe2x80x9ctime switchxe2x80x9d including a highway selector in the output highway of the time division switch so as to simultaneously read out an information memory, feed a control signal to the selector, and select one-bit information within a time slot, thus realizing the sub rate switch.
FIG. 6 is a block diagram showing a configuration example for implementing the method disclosed in the aforementioned prior art document. As shown in FIG. 6, in the prior art method, no de-multiplexing circuit and no multiplexing circuit are provided for replacing a sub rate channel and a full rate channel with each other at the input and the output of the time division switch.
Accordingly, when switching a 64-Kbps full rate channel, it is necessary to switch eight channels of the 8 kilo bit/second (Kbps). Moreover, even when switching 16-Kbps sub rate channel, it is necessary to switch the 8 Kbps sub rate channel for two channels.
This processing amount of the communication path switching control is increased, thus lowering the processing capacity of the control apparatus.
Moreover, depending on the speed of the channel to be contained, the time division switch size is changed. This makes it difficult to calculate the time division switch size required for the line exchanger. This result in deterioration of the call loss due to insufficient facility or cost increase due to an excessive facility.
It is therefore an object of the present invention to enable, in a line exchanger containing a highway of 64 Kbps full rate channels multiplexed and a highway of 16-Kbps and 32-Kbps sub rate channel multiplexed, to increase the communication path switching control speed so as to easily and accurately calculate the time division switch size.
The present invention provides a communication path switching apparatus comprising: a highway multiplexing full rate channels of a first transfer rate; a highway multiplexing sub rate channels of a second transfer rate lower than the first transfer rate multiplexed; a time division switch for performing switching control; a first conversion circuit, provided at an input of the time division switch, for replacing the sub channel of the second transfer rate with the full rate channel of the first transfer rate; and a second conversion circuit, provided at an output of the time division switch, for replacing the full channel of the first transfer rate with the sub rate channel of the second transfer rate.
Moreover, the time division switch can perform switching control always on the full rate channel basis of the first transfer rate.
Moreover, the first conversion circuit can successively convert a serial data of the highway of the sub rate channels multiplexed, into parallel data of a predetermined number of bits; add an invalid data to each of the divided parallel data of the predetermined number of bits, so as to obtain parallel data of the predetermined number of bits, thus converting the data into a serial data of the highway of full rate channels of the first transfer rate multiplexed.
Moreover, the second conversion circuit can successively convert a plurality of serial data of the highway of the full rate channels multiplexed, into parallel data of a predetermined number of bits; remove an invalid data from each of the parallel data and connect valid data of the parallel data, thus converting the data into a serial data of the highway of sub rate channels of the second transfer rate multiplexed.
Moreover, the first transfer rate may be 64 K bits per second.
Moreover, the second transfer rate may be at least one of 32 Kbps, 16 Kbps, and 8 Kbps.
According to another aspect of the present invention, there is provided a communication path switching method in a communication path switching apparatus comprising: a highway multiplexing full rate channels of a first transfer rate; a highway multiplexing sub rate channels of a second transfer rate lower than the first transfer rate; and time division switch for performing switching control; said method including: a step of replacing the sub channel of the second transfer rate with the full rate channel of the first transfer rate at an input side of the time division switch; and a step of replacing the full channel of the first transfer rate with the sub rate channel of the second transfer rate at an output side of the time division switch.
According to still another aspect of the present invention, there is provided a computer program product for controlling the aforementioned communication path switching system.
In the communication path switching apparatus, the communication switching method, and computer program product for controlling communication path switching system according to the present invention, a sub channel is replaced by a full rate channel at the input side of the time division switch, and full rate channel is replaced by a sub rate channel at the output side of the time division switch.